Lactic Acid Bacteria in Functional Diarrheal Disorders

Efficacy of Lactic Acid Bacteria in Managing Diarrhea-Associated Functional Gastrointestinal Disorders: A Randomized Controlled Trial

The goal of this clinical trial is to learn whether a probiotic supplement can improve symptoms and quality of life in adults with diarrhea-predominant irritable bowel syndrome (IBS-D) or functional diarrhea (FD). These conditions can cause frequent loose stools, abdominal discomfort, and a lower quality of life.

The main questions this study aims to answer are:

• Does the probiotic improve quality of life compared with a placebo (a look-alike capsule that contains no active bacteria)?
• Does the probiotic help participants have more normal stool consistency and fewer bowel movements?
• Is the probiotic safe and well tolerated in people with IBS-D or FD?

Researchers will compare the probiotic supplement with a placebo to see whether the probiotic improves symptoms and quality of life.

Participants will:

• Take either the probiotic or placebo capsule once daily for 3 months.
• Switch to the other study treatment for an additional 3 months.
• Complete quality-of-life questionnaires at the start of the study, after 3 months, and after 6 months.
• Record the number of bowel movements each day throughout the study.
• Record stool consistency each day using the Bristol Stool Form Scale.
• Record daily pain during bowel movements using a Visual Analog Scale (VAS).
• Report any medications they take and any health problems that occur during the study.

The study will follow each participant for 6 months. Researchers hope the results will help determine whether this probiotic is a useful treatment option for people living with IBS-D or functional diarrhea.

Study Overview

• Status: Recruiting
• Conditions: Functional Diarrhea; IBS (Irritable Bowel Syndrome); IBS-D (Diarrhea-predominant)
• Intervention / Treatment: Dietary supplement: LL1500; Other: Placebo Capsule

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Tamás Molnár; Phone Number: +36-62-545-189; Email: molnar.tamas@med.u-szeged.hu

Study Locations

• Hungary
  • Szeged, Hungary, 6725
    • Recruiting
    • University of Szeged
    • Contact: Tamás Molnár; Phone Number: +36-62-545-189; Email: molnar.tamas@med.u-szeged.hu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Adults aged 18 years or older.
• Have diarrhea-predominant irritable bowel syndrome (IBS-D) or functional diarrhea (FD) diagnosed using Rome V criteria.
• Have had symptoms for at least 6 months.
• Have no warning signs that suggest another digestive disease.
• Have been taking the same treatment for IBS-D, FD, and other medical conditions for at least 1 month before joining the study.
• Are willing and able to provide written informed consent and follow study procedures.

Exclusion Criteria:

• Took antibiotics or probiotic products within the past 4 weeks.
• Had abdominal surgery in the past, except appendix removal (appendectomy).
• Have another type of irritable bowel syndrome or another functional digestive disorder.
• Have a known digestive disease that may explain their symptoms.
• Plan to start a new medication or change the dose of an existing medication during the study (except antispasmodic medications).
• Are unable or unwilling to complete study questionnaires and daily symptom records.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Experimental First Arm; Participants randomized to this arm will receive LL1500, a probiotic supplement containing Lactobacillus rhamnosus and Lactobacillus plantarum, once daily for 3 months, followed by crossover to matching placebo for an additional 3 months under double-blind conditions.	Dietary supplement: LL1500; LL1500 is an oral probiotic supplement administered once daily as a gelatin capsule. Each capsule contains lyophilized Lactobacillus rhamnosus and Lactobacillus plantarum, providing at least 7.5 × 10⁹ colony-forming units (CFU) of each bacterial strain. Participants will receive LL1500 for a 3-month treatment period.; Other: Placebo Capsule; Matching oral placebo administered once daily as a gelatin capsule containing inactive excipients and no live bacterial strains. Participants will receive placebo for a 3-month treatment period.
Placebo Comparator: Placebo First Arm; Participants randomized to this arm will receive matching placebo once daily for 3 months, followed by crossover to LL1500, a probiotic supplement containing Lactobacillus rhamnosus and Lactobacillus plantarum, for an additional 3 months under double-blind conditions.	Dietary supplement: LL1500; LL1500 is an oral probiotic supplement administered once daily as a gelatin capsule. Each capsule contains lyophilized Lactobacillus rhamnosus and Lactobacillus plantarum, providing at least 7.5 × 10⁹ colony-forming units (CFU) of each bacterial strain. Participants will receive LL1500 for a 3-month treatment period.; Other: Placebo Capsule; Matching oral placebo administered once daily as a gelatin capsule containing inactive excipients and no live bacterial strains. Participants will receive placebo for a 3-month treatment period.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Irritable Bowel Syndrome Quality of Life (IBS-QOL) Total Score at 3 Months	IBS-specific quality of life assessed using the Irritable Bowel Syndrome Quality of Life (IBS-QOL) questionnaire. The IBS-QOL contains 34 items and yields a total score ranging from 0 to 100, with higher scores indicating better quality of life. The outcome measure is the change in total IBS-QOL score from baseline to 3 months.	Three months after enrollment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Irritable Bowel Syndrome Quality of Life (IBS-QOL) Total Score at 6 Months	IBS-specific quality of life assessed using the Irritable Bowel Syndrome Quality of Life (IBS-QOL) questionnaire. The IBS-QOL contains 34 items and yields a total score ranging from 0 to 100, with higher scores indicating better quality of life. The outcome measure is the change in total IBS-QOL score from baseline to 6 months.	Six months after enrollment
Mean Daily Stool Frequency at 3 Months	Mean number of bowel movements per day recorded by participants. The outcome measure is the change in average daily stool frequency from baseline to 3 months. Lower values indicate fewer bowel movements.	Three months after enrollment
Mean Daily Stool Frequency at 6 Months	Mean number of bowel movements per day recorded by participants. The outcome measure is the change in average daily stool frequency from baseline to 6 months. Lower values indicate fewer bowel movements.	Six months after enrollment
Mean Bristol Stool Form Scale Score at 3 Months	Stool consistency assessed using the Bristol Stool Form Scale, which ranges from Type 1 (hard stools) to Type 7 (watery stools). Types 3 to 5 are considered normal stool consistency. The outcome measure is the change in mean Bristol Stool Form Scale score from baseline to 3 months.	Three months after enrollment
Mean Bristol Stool Form Scale Score at 6 Months	Stool consistency assessed using the Bristol Stool Form Scale, which ranges from Type 1 (hard stools) to Type 7 (watery stools). Types 3 to 5 are considered normal stool consistency. The outcome measure is the change in mean Bristol Stool Form Scale score from baseline to 6 months.	Six months after enrollment

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Defecation Pain Visual Analog Scale (VAS) Score at 3 Months	Pain during defecation assessed daily using a Visual Analog Scale (VAS). Scores range from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. The outcome measure is the change in mean daily VAS score from baseline to 3 months.	Three months after enrollment
Defecation Pain Visual Analog Scale (VAS) Score at 6 Months	Pain during defecation assessed daily using a Visual Analog Scale (VAS). Scores range from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. The outcome measure is the change in mean daily VAS score from baseline to 6 months.	Six months after enrollment
Treatment-Emergent Adverse Events	Number of participants experiencing any adverse event reported during treatment with either the probiotic supplement or placebo. Adverse events will be collected throughout study participation.	From enrollment through 6 months

Collaborators and Investigators

• Sponsor: Szeged University

Study record dates

Study Major Dates

• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): November 1, 2028
• Study Completion (Estimated): November 1, 2029

Study Registration Dates

• First Submitted: October 29, 2026
• First Submitted That Met QC Criteria: October 29, 2026
• First Posted (Actual): November 4, 2026

Study Record Updates

• Last Update Posted (Actual): November 4, 2026
• Last Update Submitted That Met QC Criteria: October 29, 2026
• Last Verified: October 1, 2026

More Information

Terms related to this study

• Keywords: IBS; probiotic; supplement; IBS-D; FD
• Additional Relevant MeSH Terms: Intestinal Diseases; Digestive System Diseases; Gastrointestinal Diseases; Colonic Diseases; Colonic Diseases, Functional; Irritable Bowel Syndrome
• Other Study ID Numbers: NNGYK/09884-2/2026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No